Muxtape has been out for four or five months. A couple weeks ago, I was being held captive in my own apartment (building maintenance was painting both sides of my front door) and I finally got around to uploading a mix. You can upload up to twelve tracks at 24mb a piece, and it creates a streaming mix for you to send to your friends, lovers or SOs. Whomever.
If you're interested, you can find my mix here: http://robothero.muxtape.com/. Post yours, too!